diff --git a/tools/spec_parser/Dart.g b/tools/spec_parser/Dart.g
index 248d74debdd..594dae4e550 100644
--- a/tools/spec_parser/Dart.g
+++ b/tools/spec_parser/Dart.g
@@ -4,6 +4,9 @@
 
 // CHANGES:
 //
+// v0.35 Change named optional parameter syntax to require '=', that is,
+// remove the support for ':' as in `void f({int i: 1})`.
+//
 // v0.34 Add support for inline classes.
 //
 // v0.33 This commit does not change the derived language at all. It just
@@ -371,7 +374,7 @@ defaultFormalParameter
     ;
 
 defaultNamedParameter
-    :    REQUIRED? normalFormalParameter ((':' | '=') expression)?
+    :    REQUIRED? normalFormalParameter ('=' expression)?
     ;
 
 typeWithParameters